The present invention relates to a multiphase SCR (semi-conductor controlled rectifier) d.c. interrupter, used for regulation of input or output power of electric loads, especially electric motors being use from direct current sources.
Existing SCR direct current interruptors require use of sophisticated control circuits and additional commutating (switching) semi-conductor controlled rectifiers, which increase interrupter weight and cost.
D.C. interrupters without the commutating SCRs are already known in the art. These are the single-phase interrupters, operating as pulse repetition frequency modulators with one SCR and a resonant parallel arm, the latter containing a reactor (inductance) and a capacitor (capacitance) or a current transformer performing as autotransformer and capacitor.
The semi-conductor controlled rectifier d.c. interrupter according to this invention is distinguished by the fact that it comprises any number of identical, parallel and self-contained phases, each of them being a series connection of SCRs and diodes, where the resonant arms are connected in star Y-connection and have series capacitors and reactors so that the star vertices (leads) are associated with the SCR cathodes and the diode anodes whereas the star neutral is connected with positive or negative pole of the d.c. power source. The diodes whose cathodes are connected in star Y-connection, have their anodes (star vertices) connected between the capacitors and reactors, while the star neutral (i.e. the diode cathodes) is associated -- via the resistor and contactor -- with the d.c. power source negative pole as well as with the cathode of one diode and the anode of the other diode. These diodes are connected in series. One of the series connected diodes has its anode associated with the d.c. power source negative pole. Its cathode and the other diode anode are connected between the armature and the excitation windings; the other diode cathode is connected between the excitation winding and the cathodes of the diodes which are connected in series with the semi-conductor controlled rectifiers. Between the d.c. motor and the d.c. power source negative pole, the latter being connected with anode of one of the diodes connected in series, the main contactor is introduced; between the d.c. power source positive pole and the d.c. motor, the diode is connected so that its anode is introduced between the d.c. motor and the main contactor, its cathode being associated with the d.c. power source positive pole. The excitation winding is shunted with the resistor, and the SCRs are triggered (fired) in predetermined sequence with phase displacement 2 .pi./m.
With the SCR interrupter in accordance with the present invention, the d.c. source full voltage will be available at its output (reduced only by voltage drop across the SCR and the diode); moreover, it features high efficiency and lower harmonic content in the output current.